Earthquake Load Cases

Hi every body,

I work with CAESAR II V4.5 .
I want to know how are you considering eartquake occasional load cases in static analysis?

Assume Ux, Uy and Uz as static uniform loads due to earthquake, each of them along each axis and y-axis is vertically.

I consider occasional load cases, due to earthquake, in two ways, simultaneously:
first along each axis: W+P+T±Ux, W+P+T±Uy and W+P+T±Uz.
and second in two vertical planes: W+P+T±Uy±Ux and W+P+T±Uy±Uz.

Please, tell me which of them is prefered and why, or there is some other ways that I don't know, or I could go on as I described before!?

Looking forward your comments.

With High Pleasures.
Bye.

M. Sami

Hi

Are you entering a seismic load or are you entering a seismic coefficient? (which is location specific).

Also what are you setting up the combinations for, ie is it for code complaince (if so then which code) or is it for operating loads?

Hi,
a) I enter a seismic acceleration equal to 0.35g, which is location specific.

b) It is for operating loads.

c) I work with B31.3 .

thank you,

Bye.

Dear Mr Sami,
For static seismic analysis, we build the load cases as follows:

CASE 1 (OPE) W+D1+T1+P1
CASE 2 (OPE) W+D2+T2+P2
CASE 3 (SUS) W+P1
CASE 4 (SUS) W+P2
CASE 5 (OPE) W+D1+T1+P1+Ux
CASE 6 (OPE) W+D1+T1+P1-Ux
CASE 7 (OPE) W+D1+T1+P1+Uz
CASE 8 (OPE) W+D1+T1+P1-Uz
CASE 9 (EXP) L13=L1-L3 (Algebraic)
CASE 10 (EXP) L14=L2-L4 (Algebraic)
CASE 11 (OCC) L15=L5-L1 (Algebraic)
CASE 12 (OCC) L16=L6-L1 (Algebraic)
CASE 13 (OCC) L17=L7-L1 (Algebraic)
CASE 14 (OCC) L18=L8-L1 (Algebraic)
CASE 15 (OCC) L23=L3+L11 (Scalar)
CASE 16 (OCC) L24=L3+L12 (Scalar)
CASE 17 (OCC) L25=L3+L13 (Scalar)
CASE 18 (OCC) L26=L3+L14 (Scalar)

T1, P1 = Operating temperature & pressure.
T2, P2 = Design temperature & pressure.
Seismic acceleration in vertical direction ( Uy )is normally neglected in static seismic analysis. Case 5 to 8 are seismic in operating condition and case-15 to 18 are for code compliance (OCC stress). Case-11 to 14 take care of non-linearity of the system.

Regards,
Manoj Sarkar

Seismic load cases combination we do it so:
Ux+Uy+Uz. This is a short calculation an conservativ.
Or the maximum from
Ux+Uy ; Uz+Uy
For the pipe stress calculation the sign (-Ux or +Ux)are not so imported.
For the stress calculation in the pipe only use
primary loads like pressure and weights and not temperature.
The restraint load calculation must with include temperature.
Here change the sign from the dynamic part
for the combination with the static load and look for the maximum.

Hi Morteza

We set our loads up in exactly the same way as Manoj does above. We also ignore the vertical seismic component.

Hi every body

Thank u very much for ur answeres.

bye.